Need help with a lab?

Question

Okay, I did a lab in class, but I'm having a little trouble with answering the questions about the lab... so your help would be much appreciated.

Okay, so first I added NH4OH, AgNO3 and glucose to a test tube.I saw that silver was coating the inside of the test tube, but the question is:

1. *Explain how the presence of glucose allowed this coating to form*

I thought the reaction of NH4OH and AgNo3, would produce NH4NO3 and AgNo3 (a precipitate), but apparently ther's more to it. I just really don't know where to add the C6H12O6 into the equasion. I don't need the equasion, I just need to understand what glucose has to do with it.

And I also have another question....
I added 5ml of Benedict's solution (it detects reducing sugars such as glucose and fructose) to 5 test tubes. THen to each of those 5 test tubes I added 8 drops of 2% glucose solution. I then heated the mixtures for ...

Guaranteed "best answer" to the most helpful answer.

Thanks in advance

continuation of second question)

I heated the mixtures for 5 minutes, and theyy were all different colors, even though I put the same thing in all of the test tubes...

The question is

"Chances are that each of your five test tubes was identical in appearence, but they may not have been. Suppose they had not all been the same color. Make a bypothesis to account for this.


Oh, and I posted this in the chemistry section, but this lab is actually from biology class.

Answer 1

The silver mirror is a test for aldehydes called the Tollens Test for Aldehydes. The glucose was the aldehyde. See the first reference below:

The results of the Benedict's solution test is a measure of how precise your experimental actions were. The more each act is done "the same" the closer the final results will be (the formation of a red copper compound). If your results were all different then you either did a poor job measuring the reactants or did something different when heating each tube.